This invention relates to a rare earth-containing alloy and a method for the purification of hydrogen gas with the alloy.
Hydrogen gas is a very important industrial material and is produced by several methods, such as, cracking of natural gas or petroleum, electrolysis of water, catalytic decomposition of ammonia and water gas reaction. It is usual that the hydrogen gas produced by the above methods contains various kinds of impurities including rare gases, such as, helium, argon, xenon and krypton, inorganic gases, such as, oxygen, nitrogen, carbon monoxide, carbon dioxide, sulfur dioxide, ammonia and water, and organic gases, especially hydrocarbon gases, such as, methane and ethane. Therefore, it is a usual practice that the hydrogen gas is subjected to a purification process in accordance with the use for which the gas is employed.
Several ways of purification of hydrogen gas are known. One example proposes to purify hydrogen gas by adsorption on an adsorbent, such as, zeolites, active charcoal, active alumina and silica gel at a low temperature of, say, liquid nitrogen. Another example proposes to purify hydrogen gas by a pressure cycle for the adsorption and desorption of the hydrogen gas on and from the same adsorbents as in the above example at room temperature. A further example proposes to purify hydrogen gas by the principle of diffusion through a membrane of a particular alloy, such as, palladium-silver and palladium-yttrium alloys. On operation, these methods are disadvantaged by a relatively high cost generally. In particular, the diffusion method has another problem in relation to the durability of the alloy membranes.